Case1 Base Case description (Output of Mesh grid)

 

 

Basic Set Up: Data File Description

The initial data file for the project is: SpatVar_002\Data\SpatVar_002_Case1.dat.   The basic data includes:

1Group data for the single formation which are assigned the "Sandstone" properties using Group_control_data and Group_data data structures.

2Material_data for an elastic Sandstone.

3Support data (Support_data) defining fixity in perpendicular direction for base and side boundaries.

4Gravity_data and Global_loads with their corresponding Time_curve_data to define all loads. Load_case_control_data to define surface load as active.

5Mesh control (Mesh_control) and Unstructured mesh generation data (Unstructured_mesh_data) defining a constant mesh size of 20m.

6Time scaling data (Time_scaling_data) with optimal time step 1E-4 Ma.

7Damping data (Damping_global_data) to define bulk damping on the effective mean stress (Bulk Viscosity model)

8Control data (Control_data) defining:

(a)  Incremental solution algorithm (Type 1),

(b)  High maximum number of time steps

(c)  Duration of t=1 Ma,

(d)  Factor of critical time step = 0.7,

(e)  Plot file output at the end of the stage and every 0.1 Ma,

(f)  Screen message output every 500 mech steps,

9Geometry data (nodal_data, Geometry_line and Geometry_surface) for definition of the 2D geometry.

 

The Group_data data structure is compulsory and defines the properties for each geometry group.  For this example these comprise:

1The name of the group.

2The element type.

3The material assigned to the group

4The surfaces that define the geometry for the group.

5The type of porous flow

 

Data File

 

 

* Group_data  NUM=1

! ---------------------------------

 Group_name                   "Sandstone"

 Element_type                       TPM3V

 Material_name                "Sandstone"

 Porous_flow_type                       1

 Surfaces               IDM=1

    1

 

 

1A single group is defined using the TPM3V (3 node plane strain triangular elements using the average Volume formulation).  

1The material assigned to this element group is "Sandstone".

2The geometry of the group is defined by surface 1.

3The simulation will be performed using the porous flow type number 1 (dry porous material).

 

The Group_control_data  data structure is compulsory and defines:

1The groups number of geometry groups in the problem, where each geometry group relates to a region with specific properties; e.g. regions with different material assignments, individual stratigraphy layers, etc.

2Whether the group is active or inactive in the fields; i.e. geomechanical, porous flow, thermal, that are being solved.

 

Data File

 

 

* Group_control_data

! ---------------------------------

 Group_numbers                 IDM=1

   1

 Active_geomechanical_groups   IDM=1

   1

 

A single group is present in the simulation with the geomechanical active.

 

The material properties for the material "Elastic" as well as its associated fluid properties are defined in the datafile.

 

Data File

 

 

* Material_data NUM=1

! ---------------------------------

 Material_name     "Sandstone"

 Units IDM=4

  /Stress/                       "MPa"

  /Length/                         "m"

  /Time/                           "s"

  /Temperature/              "Celsius"

 Isotropic_elastic_properties     IDM=2

  /Young's Modulus/              5000

  /Poisson's Ratio/              0.200

 Grain_density                     2710  ! (Kg/m3)

 Porosity                          0.35  

 

1A single material is used for the simulation.

2The material is named "Sandstone".

3The material is isotropic elastic with a Young's Modulus of 5 GPa and a Poisson's Ratio of 0.2.

4Reference Porosity is 0.35 and grain density is 2710 kg/m3

 

 

The support data is used to define the fixity in perpendicular direction for base and side boundaries.

 

Data File

 

 

* Support_data

! ---------------------------------

 Displacement_codes IDM=2 JDM=2

  /"Set 1"/    1 0

  /"Set 2"/     0 1

 Displacement_code_lines IDM=3  JDM=2

        /Lines/        1 2 4

  /Assign Set/    2 1 1

 

1Two displacement code sets are defined.

2The corresponding displacement code sets are assigned to each boundary (via line assignment) in order to fix displacement in perpendicular directions.

 

 

Gravity data and its corresponding time curve is defined so that gravity is gradually applied during the first control stage (1 Ma) using and S-curve.

 

Data File

 

 

* Gravity_data

! ---------------------------------

 Gravity_constant     9.810

 Load_curve             100

 

 

* Time_curve_data NUM=100

! ---------------------------------

 Time_curve  IDM=2

   0.0  1.0

 Load_factor   IDM=2

   0.0  1.0

 Curve_type       2 ! S-Curve

 

1Gravity constant is defined.

2Time curve number 100 is assigned.

3Time curve 100 is defined so that full load is applied gradually over the duration of the first control stage (1 Ma)

4A S-curve type is used for smooth application of the load

 

 

 

Loading data to apply a load to the top surface of 20 MPa is defined

 

Data File

 

 

* Global_loads                NUM=1

! ---------------------------------

 Surface_load  IDM=2 JDM=1

  /set 1/  20    0

 Surface_load_type         1

 Surface_load_line_pointers IDM=1 JDM=2

  /Lines/        3

  /Assign Set/   1

 

* Time_curve_data             NUM=1

! ---------------------------------

 Time_curve    IDM=2

   1.0          1.9

 Load_factor   IDM=2

   0.0   1.0

 Curve_type    2                

 

* Load_case_control_data

! ---------------------------------

 Loadcases   IDM=1

  1  

 Active_load_flags IDM=1

  2

 

1A normal load of 20 MPa is defined via a Surface_load set.

2Surface load type is set to 1 (surface load in local coordinate system of facets).

3Load is assigned to line 3 (top surface)

4Time curve number 1 (which is automatically assigned to Global_loads NUM=1) is defined so that full load is applied at 1.9 Ma

5A S-curve type is used for smooth application of the load

6Load_case_control_data is defined to define load 1 as active

 

 

 

An "unstructured mesh" with 300m size plane strain triangular elements is defined for this example.

 

Data File

 

 

* Mesh_control_data

! ---------------------------------

 Generation_algorithm  2

 

 

* Unstructured_mesh_data

! ---------------------------------

 Default_element_size       20

 Element_size_bounds  IDM=2

  /Max. Element Size/       20

  /Min. Element Size/       20

 

1The algorithm used for this simulation is set to 2  (i.e. unstructured mesh).

2The element size is set to 20 m.

 

 

The mechanical step size is defined via Time_scaling_factors data structure. The Optimal_time_step keyword has been used. It is the most simple way of defining the mechanical time step size and is generally recommended. Using this method the mass scaling is computed automatically.

 

Data File

 

 

* Time_scaling_factors

! --------------------------------------

 Optimal_time_step              1.0E-04

 

An optimal time step of 1.0·10-4 Ma is defined

 

 

 

Bulk viscosity damping  is defined in order to damp the compression part of the dynamics-related oscillations on the effective mean stress.

 

Data File

 

 

* Damping_global_data

! ---------------------------------

 Bulk_damping_model         "BulkViscosity"

 Bulk_damping_properties              IDM=1

   0.50000  

 

A bulk viscosity model with a bulk viscosity constant of 0.5 is used in this example in order to damp the compressive oscillations due to dynamics in the effective mean stress. This is a generally recommended set up for most of ParaGeo geomechanical analysis. (For more information on the bulk viscosity model see damping_global_data).

 

The current analysis considers two control stages with identical data defined by the Control_data structure in which control data for the geomechanical fields is provided.  For more information see Solution Control Data.

 

Data File

 

 

* Control_data

! --------------------------------------

 Control_title                     "Gravity"

 Solution_algorithm                       1

 Factor_critical_time_step              0.5

 Maximum_number_time_steps          1000000

 Termination_time                       1.0

 Output_frequency_plotfile               -1

 Output_time_plotfile                   0.1

 Screen_message_frequency               500

 

 

1Duration for control stage is set to 1.0 Ma is defined.

2The solution algorithm is set to number 1, i.e. Transient dynamic algorithm.

3The maximum number of time steps is set to 1000000 (high so that simulation is not interrupted).

4The factor critical time step is set to 0.7 so the time step used for the simulation will be 0.7 ·  1.0·10-4.

5Information will be displayed on the screen (command prompt) every 500 mech steps.

6A plot file is requested every 0.1 Ma (Output_time_plotfile=0.1) and at the end of the stage (Output_frequency_plotfile=-1).

 

 

Data structure Spatial_grid_output is used to define the grid to be exported in a .spat file.

 

Data File

 

 

* Spatial_grid_output  NUM=1

! ---------------------------------

 Name               "Complete_Domain"

 File_name               "OutputGrid"

 Grid_name_flag                    1

 Geometry_entity_flag              0  

 Element_variables       IDM=5

  "Strs_xx"  

 "Strs_yy"  

 "Strs_xy"

  "Press"    

 "Efstrs"

 

 

1Name of the spatial grid is defined as "Complete_Domain".

2The file name is defined as OutputGrid (if not defined the model name would be used instead). Because Grid_name_flag is set to 1 the grid name will be added to the file name. Thus the exported file will be named "OutputGrid_Complete_Domain.spat"

3Geometry_entity_flag is set to 0 to do not export geometry IDs into the file.

4The variables to be exported into the grid are defined. They are Stress in X and Y directions, Shear stress in XY plane, Effective Mean Stress (Press) and deviatoric stress (Efstrs).

5Because grid type is not specified, type of output grid will be "Group" (a grid consisting in the same ParaGeo mesh as used for the model defined on a group by group basis).

 

 

A summary of the data for defining the 2D geometry for this example is presented bellow. These data comprise nodal_data, Geometry_surface and Geometry_line data structures.

 

Nodal_data

Data File

 

 

* nodal_data  

 node_number IDM=4

  1  2  3  4  

 coordinates IDM=3 JDM=4

 0.0    0.0     0.0

 100.0  0.0     0.0

 100.0  1000.0  0.0

 0.0    1000.0  0.0

 

1Four nodes are required to define the column geometry

 

 

 

Surfaces

Data File

 

 

* geometry_surface NUM=1

 lines        IDM=4

  1 2 3 4

 

 

1A single surface is required to define the model domain. Such surface is defined by four lines.

 

 

 

Lines

Data File

 

 

* geometry_line NUM=1

 line_type      1

 points        IDM=2

  1 2

 

* geometry_line NUM=2

 line_type      1

 points        IDM=2

  2 3

 

* geometry_line  NUM=3

 line_type      1    

 points     IDM=2

   3  4  

 

* geometry_line  NUM=4

 line_type      1    

 points     IDM=2

   4  1  

 

1Four lines are defined.

 

 

 

 

Results

The result files for the project are in directory: SpatVar_002\Results. The file "OutputGrid_Complete_Domain.spat" contains the grid data consisting of:

1) Spatial_grid data defining the groups for which a grid is exported and the name of the variables in the grid

2) Spatial_grid_group data where mesh topology, node coordinates and values for the variables at elements is provided.

 

OutputGrid_Complete_Domain.spat

Data File

 

 

* Spatial_grid NUM=1

! ----------------------------------------

 Name                     "Complete_Domain"

 Type                     "Group"

 Groups                           IDM=1

    "Sandstone"

 Element_variables                IDM=5

    "Strs_xx"

    "Strs_yy"

    "Strs_xy"

    "Press"

    "Efstrs"

 Auto_delete_flag                    0

 

 

 

* Spatial_grid_group               NUM=1

! ----------------------------------------

 Name                     "Sandstone"

 Group_assignment         "Sandstone"

 Grid_name                "Complete_Domain"

 Element_type             "TRIA3"

 Configuration_type       "Current"

 Element_variables                IDM=5

    "Strs_xx"

    "Strs_yy"

    "Strs_xy"

    "Press"

    "Efstrs"

 Topology                         IDM=3   JDM=622

  57    3  111

 110    1  112

    .

    .

    .

 328  367  251

 Node_numbers                     IDM=367

   1    2    3    4    5    6    7    8    9   10

  11   12   13   14   15   16   17   18   19   20

    .

    .

    .

 361  362  363  364  365  366  367

 Coordinates                      IDM=2  JDM=367

   0.00000        0.00000    

   100.000        0.00000    

    .

    .

    .

   49.2221        835.761

 Element_values                   IDM=5  JDM=622

  -5.06078   -20.1848  0.138721E-01   -10.0982    15.1299    

  -9.26258   -37.1111  -0.209789E-01  -18.5495    27.8424  

    .

    .

    .

  -5.67052   -22.6729  -0.138595E-01  -11.3374    7.0033  

 

 

1Spatial_grid data is defined.

2Type is set to "Group" (ParaGeo mesh on a group by group basis).

3Groups with grid data are defined. In this case there is only one group named "Sandstone".

4The Element_variables for which the grid contains values are specified.

5Auto_delete_flag = 0 means that grid will be automatically deleted after being used by ParaGeo for any other operation (if loaded to any other ParaGeo model).

 

 

 

 

6Spatial_grid_group data which contains the grid with variable values for the group "Sandstone" is defined.

7The element type of the grid are Triangles.

8Configuration_type "Current" means that values exported to the grid correspond to values at the time of export (in this case at the end of the analysis).

9The Element_variables for which the grid contains values are specified.

10The topology for all the grid elements is defined. There is a total of 622 elements in the grid with each element being composed of three nodes.

11Node numbers are provided.

12Node coordinates for the 367 nodes are provided. Each row correspond to each node specified in node_numbers following the same order (i.e. row 12 are coordinates for the 12th node specified in Node_numbers, which in this case is node number 12).

13Values at each element for the five specified variables are provided. Each column correspond to the variables specified in Element_variables following the same order. Each row correspond to each element defined in Topology following the same order.

 

 

 

 

 

SpatVar_002_Case1_Results

 

Results for the exported variables.